Industrial production of toner generally occurs through batch reactions. For example, is an emulsion/aggregation (EA) scheme, two reactors can be used, one batch reactor to accommodate particle formation and aggregation and then the slurry is transferred to a second batch reactor to finish the product by coalescence. The residence time of the reaction mixture in either tank can be about the same, and may range up through 8 hours or more.
A continuous process, if possible, can provide advantages over more conventional batch reactions by providing one or more of faster, efficient mixing, selectivity enhanced side products, reduced secondary reactions and side products, higher yield, fewer impurities, extreme reaction conditions, time and cost savings, and increased surface area to volume ratio that results in good mass and heat transfer.
Continuous processes however, do have some shortcomings, for example, because of the need for reactant and product communication devices, there is a risk of blocking such conduits with reactants and/or products. Hence, reactions that produce a solid product or side product, such as, solid halide salts, such as, sodium bromide, produced in a Buchwald reaction, toner particles and so on may not be amenable to a continuous process. Also, a continuous process may not yield a product suitable for comparable commercial use because of, for example, altered reaction kinetics.